Load detector for elevator cage

Abstract

A load detector for an elevator having a cage moving up and down in a shaft for transporting passengers and a cable hanging the cage, including a relative position detector configured to detect a relative position of the cage against the shaft; and a calculator configured to calculate a change of the relative position between the position of the cage just after landing at a floor and the position of the cage just before leaving the floor, and a load of the cage on the basis of the change of the relative position caused by an expansion and contraction of the cable.

What is claimed as new and desired to be secured by Letters Patent of the United States is:  
     
       1. A load detector for an elevator having a cable placed around a sheave driven by a motor, said cable hanging a weight and a cage moving up and down in a shaft for transporting passengers, comprising: 
       a brake having a housing, a brake disk secured to a rotary shaft of said motor, and a brake shoe for pressing said brake disk toward an elastic ring disposed between said brake shoe and the inside wall of said housing and stopping the revolution of said sheave;  
       a strain detector attached to said elastic ring and configured to detect a torsional strain of said brake disk caused by an unbalance in weight between said cage and said weight; and  
       a calculator configured to calculate a change of said torsional strain between a torsional strain just after said cage lands at a floor and a torsional strain just before said cage leaves said floor, and a load of said cage on the basis of said change of said torsional strain.  
     
     
       2. A load detector for an elevator having a cable placed around a sheave driven by a motor, said cable hanging a cage through a hanging sheave attached to said cage moving up and down in a shaft for transporting passengers, comprising: 
       a strain detector configured to detect a strain of a rotary shaft of said sheave caused by a bending force (F 2 ) applied perpendicular to and intersecting the axis of said rotary shaft; and  
       a calculator configured to calculate a load of said cage on the basis of said strain.  
     
     
       3. A load detector for an elevator having a cable placed around a sheave driven by a motor said cable hanging a cage through a hanging sheave attached to said cage moving up and down in a shaft for transporting passengers, comprising: 
       a strain detector configured to detect a strain of a shaft of said hanging sheave caused by a bending force (F 2 ) applied perpendicular to and intersecting the axis of said rotary shaft; and  
       a calculator configured to calculate a load of said cage on the basis of said strain.